Method and arrangement for artillery missiles

ABSTRACT

The present invention relates to a method and an arrangement for shells ( 1   a,    1   b ) fired from launch weaponry, using some of the barrel pressure built up in the barrel during the launch phase for an additional active function over and above that of giving the shell ( 1   a,    1   b ) in question its trajectory velocity. According to the invention, during the launch phase, some of the propellant powder gas accelerating the shell is therefore introduced into a chamber ( 12, 38, 60 ) which is arranged in the same and which is delimited in at least one direction by an element ( 8, 31, 58, 52, 53 ) which is movable relative to the rest of the shell and on which the barrel pressure acting on the shell simultaneously acts to maintain the original direction as long as the shell is located inside the barrel during the launch phase. This technique can thus be used to remove protective casings covering the fins, in order to push out fin units and to deploy initially retracted fins.

[0001] The present invention relates to a method and an arrangement forproducing a relative displacement of specific elements included inartillery missiles, this relative displacement being intended to beactivated as soon as the missile has left the barrel from which it hasbeen fired.

[0002] The invention is in the first instance intended to be used inthose artillery missiles which are fired without rotation or at a lowinherent rotation about their longitudinal axis, and which, forstabilizing them in the continued trajectory towards the target, areassumed to be provided with stabilizing fins which are arranged at therear end and are initially retracted until the missile has completelyexited the launch arrangement from which it has been fired, and then aredeployed once it has left the launch arrangement. To guide the missilesin their trajectories in pitch and yaw towards their intended targets,they can also be provided with guide members arranged for this purposepreferably at their front end and deployable more or lesssimultaneously.

[0003] Airborne missiles can be rotation-stabilized in their trajectoryor stabilized in another way, for example by means of fins.Rotation-stabilized missiles have steady trajectories and they can bemade mechanically simple since the launch arrangement as a rule isresponsible for ensuring that the missile acquires the necessary initialrotation. However, the high rotational velocity has at least hithertomade it impossible to provide this type of missile with awell-functioning guidance system. When work is undertaken today todevelop effective guidable missiles, one has therefore concentratedefforts on missiles which do not rotate at all, or rotate only slowly,about their own longitudinal axis and which are aerodynamicallystabilized by means of fins arranged in their rear part.

[0004] In addition to stabilizing the missile flight, the stabilizingfins, in a fin-stabilized nonrotating missile, or in a missile rotatingonly slowly, can additionally, if they are arranged for this purpose,give rise to an active lifting force which acts on the missile and canbe used to increase its range of fire.

[0005] A current trend in the development of artillery technology istowards new long-range artillery missiles guided in their final phase,and interest has increased in different types of fin-stabilized shellsintended for firing in conventional guns and howitzers. To make itpossible to launch fin-stabilized shells with a low inherent rotationdirectly from grooved barrels, the shells need to be provided with adrive band as their only direct contact with the grooving of the barrel.The same gun or howitzer can thus be used, without special intermediatemeasures, to successively fire essentially nonrotating shells providedwith drive bands and with stabilizing fins, which can be deployed intrajectory, and entirely conventional rotation-stabilized shells.

[0006] In controlling the trajectory of fin-stabilized missiles such asshells, rockets and projectiles, it is necessary to know and be able tocontrol the roll position of the missile. This in order to be able tocontrol the missile in pitch and yaw. This control is achievedpreferably with special control elements, for example in the form ofmovable nose fins, so-called canard fins, or jet nozzles. The rollcontrol moment which such control members in the front part of themissile give rise to can however in many cases be counteracted orcompletely eliminated by the guide fins in the rear part of the missile,unless special measures are taken. This is due to the fact that thevortices caused by the control moment from the rudder or other controlactivity impact the fins and this in turn gives rise to a counteractingmoment.

[0007] A way of solving this problem which has already been tested to anat least limited extent is to let the part of the missile in which thefins are secured constitute a unit which can rotate freely in relationto the rest of the missile about an axis concentric with thelongitudinal axis of the missile. In this way, the effect of the controlmoment on the fins cannot be transferred to the front part of themissile, as a result of which the missile is made easier to control.

[0008] However, the design and function of the fins are of secondaryimportance in connection with the present invention to the extent thatsaid invention does not concern the fins as such, although a preferredembodiment of this offers a method and arrangement for protecting thefins and keeping them retracted during the launch phase and releasingthem as soon as the missile in question has left the barrel of the gunor howitzer from which it is fired.

[0009] The invention can thus be applied both to those fin units whichduring the launch phase are protected by a special protective casingwhich has to be removed in order to release the fins, and in those finunits which during the launch phase are protected inside the missile andwhich, immediately after the latter has left the barrel, are pushed outbehind the original rear plane of the missile.

[0010] The basic concept of the invention is that it is possible duringthe actual launch phase, that is to say while the missile is beingdriven through the barrel of the gun, howitzer or the like from which itis being fired, to introduce some of the powder gases driving themissile from the space behind the missile into a partially closedchamber in the missile, this chamber being delimited in at least onedirection by the object, element or the like which is displaceablerelative to the rest of the missile and which is to be displaced afterthe missile has left the barrel, while the inlet through which thepowder gases are introduced into the chamber in question is sodimensioned that the high powder gas pressure inside the chamber is notable to equalize as quickly as the pressure behind the missile isequalized in relation to the surrounding atmosphere as soon as themissile has left the barrel. If correctly dimensioned, the pressureinside the chamber then gives rise to the desired relative displacementas the powder gas pressure inside the chamber acts on the displaceableobject which, when the missile has left the barrel, is no longer actedupon in the opposite direction by the rear barrel pressure.

[0011] This basic idea can then be used to release and push aside aprotective casing which during the launch phase covers the rear part ofthe missile and a fin unit included therein or in a corresponding mannerto push out a fin unit which during the launch phase has been retractedin the rear part of the missile, or to force out radially displaceablefins, or for other areas of application which fall within the scope ofthis basic idea.

[0012] The general concept of the invention is defined in the attachedpatent claims and it will now be described in more detail in connectionwith three different examples of how the invention can be used.

[0013] Of these, the first describes a method of removing a protectivecasing which initially covers the rear part of a missile and whichduring the launch phase protects an axially fixed fin unit comprisingblade fins incurved towards that part of the missile body situatedinside the casing. In this variant, the barrel pressure is introducedduring the launch phase into the casing via an opening provided anddimensioned for this purpose. As soon as the pressure behind the casingdrops, that is to say as soon as the shell has left the barrel, thepressure inside the same forces the casing off from the missile body,whereupon the hitherto incurved fins are deployed.

[0014] In the second use of the invention described below, the sameinternal barrel pressure is used to push rearwards in the direction offlight of the shell, an axially movable fin unit out from a firstposition retracted in the missile to a second position in which thefins, which can also be deployable, reach behind the original rear planeof the missile. In this variant of the invention, some of the barrelpressure during the launch phase is introduced into an inner chambersituated between the axially displaceable fin unit and the main part ofthe missile, and when the counterpressure behind the missile which alsoloads the fin unit ceases when the missile leaves the barrel, thisinternal pressure forces the axially movable fin unit out to its rearposition in the longitudinal direction of the missile.

[0015] The third example describes how the same barrel pressure is usedto release a protective casing of approximately the same type as in thefirst example and additionally at the same time to force radiallymovable fins out from a first retracted position to a second deployedposition.

[0016] However, all these examples must be seen for what they are,namely a few possible variants of practical applications of theinvention, which itself can be given other applications falling withinthe scope of the patent claims.

[0017]FIG. 1 shows a shell according to the abovementioned firstvariant, on its way towards its target,

[0018]FIG. 2 shows in longitudinal section the rear part of the sameshell as in FIG. 1, before being launched,

[0019]FIG. 3 shows the cross section along III-III in FIG. 2,

[0020]FIG. 4 shows the same details as in FIG. 2, but after launch, andwith the fins deployed,

[0021]FIG. 5 shows a partial cross section of a missile according to theabovementioned alternative two, that is to say with a fin unit which isdisplaceable in the longitudinal direction, while

[0022]FIG. 6 shows the fin unit according to FIG. 5 in the retractedposition, and

[0023]FIG. 7 shows the cross section VII-VII from FIG. 6,

[0024]FIG. 8 shows a sectional view of the rear part of a shellaccording to the abovementioned alternative three,

[0025]FIG. 9 shows a cross section along the line IX-IX in FIG. 8, and

[0026]FIG. 10 shows the same view as FIG. 8, but after the fins havebeen deployed.

[0027] The missile shown in FIG. 1, in this case the shell 1 a, isprovided with a band track 2 for a drive band (this is generally lostwhen the shell leaves the barrel), a number of deployable fins 3 whichare shown fully deployed in the figure and which are fixed on a bodypart 4 which rotates freely relative to the rest of the shell about anaxis concentric with the longitudinal axis of the shell. The dividingplane between the shell 1 and the body part 4 has been labelled 5. Inaddition, the shell 1 has two pairs of controllable canard fins 6 a, 6 band 7 a, 7 b arranged on a respective quadrant axis and with which thecourse and trajectory of the shell can be corrected in accordance withcontrol commands received either from an internal target seeker or fromthe launch site, via satellite, radar or other means. The way in whichthe shell receives control commands has nothing to do with theinvention. This question will not therefore be mentioned again below.

[0028]FIGS. 2, 3 and 4 show in greater detail how the body part 4 isconstructed. Also included here are reference labels 2 for the band and5 for the dividing plane between the body part and the rest of theshell. As will be seen from the figures, the band of the shell in thisvariant is placed on the body part 4 of the fin unit. This is because itis advantageous to have the band placed far back on a shell. The fins 3are shown in FIGS. 2 and 3 in the retracted position (see also FIGS. 1and 4) in which they are covered by a removable casing 8. In the caseshown in FIGS. 2 and 3, the casing covers the fins and also a base-bleedunit 10 which is arranged in the centre of the body part and whosecharge of slow-burning powder here has the label 11 and its gas outlethas the label 12. As will be seen from FIG. 3, the fins 3 in theretracted position are incurved towards the inside of the casing 8. Inthe casing 8 there is also a relatively narrow gas inlet 13 which uponlaunch of the shells gives the barrel pressure, i.e. the powder gasesfrom the propellant powder charge, free access to that part of theinside 40 of the base-bleed unit which is not taken up by its powdercharge 11. At the same time the inlet and outlet 13 in the casing 8 isso designed that when the shell leaves the barrel and the pressuresurrounding the shell quickly drops to atmospheric pressure, the gasexpansion reaches inside the casing by means of the fact that the inletand outlet 13 is so designed that the gases do not get out quicklyenough, resulting in the casing being removed and the fins beingreleased and deployed. This position is shown in FIG. 4. As will furtherbe seen from the figures, the body part 4 is joined to the rest of theshell via a ball bearing 14 which means that the fin unit can rotatefreely after the fins have been deployed. This does not in itself haveanything to do with the present invention even though, as mentioned inthe introduction, it does have some important advantages.

[0029] The shell illustrated in FIGS. 5, 6 and 7 is thus of the secondtype described in more general terms earlier, with a fin unit which isaxially displaceable in the longitudinal axis of the shell. Its mainpart has been labelled 1 b and it is provided in its rear part, herelabelled 29, with a drive band 2. A cavity 30 is also arranged in therear part 29 of the shell. A specially configured fin body 33 isarranged inside this cavity until the shell has left the artillery piecein which it is fired.

[0030] The fin body with its retracted fins is shown in the retractedposition in FIGS. 6 and 7. There are eight fins here and they are alllabelled 32. Each one of them lies in its own track 37 in the body part31 and they can be deployed outwards and rearwards about their axes 33,in the manner indicated by the arrows A in FIG. 7. The special fin body31 consists of a front part 34 and a rear part 35 which are rotatablerelative to each other with a ball bearing 36 which means that this finunit too spins freely in the deployed position.

[0031] The special feature of the variant of the invention describedhere is that when the shell has left the artillery piece from which itis fired the whole of the fin body 31 is displaced from its fullyretracted position in the space 30 to a position where only its frontpart 34 is left in its outlet, where it is blocked by means of adeformation joint of one type or another, while the whole of the rearpart 35 of the fin body is located behind the original rear plane B ofthe shell and where the fins 32 are deployed in the manner indicated inFIG. 6 and the rear part of the body in which they are secured isallowed to rotate freely relative to the main part of the shell aboutthe bearing 36 concentric with the longitudinal axis of the shell. Formoving the body part 31 to its rear position, propellant powder gasesare used which during the launch phase are allowed to flow via thechannel 39 into the inner chamber which is labelled 38. When the shellleaves the barrel from which it has been fired, the pressure behind thefin unit quickly drops to atmospheric pressure, while the pressureinside the chamber 38 becomes higher. As the counterpressure behind thefin unit drops, the gas quantity at a higher pressure inside the chamber38 will expand. This gives the desired displacement of the fin unit toits outer position shown in FIG. 5. However, the original pressureinside the chamber 38 should never be allowed to rise to the same levelas the barrel pressure since this would result in excessively rapid findeployment with associated risks of damage to the fin unit. The maximumpressure inside the chamber 38 is entirely dependent on what quantitiesof propellant gas leak into the chamber through the channel 39 as themissile passes through the barrel. The maximum pressure inside thechamber can thus be regulated by precise dimensioning of this channel.

[0032] A particular advantage of the push-out fin unit is that its finsreach further away from the centre of gravity of the missile than whenthe fins are secured directly at the rear end of the missile. This inturn means that the fins of the push-out fin unit can be made smallerwhile retaining the stability of the missile.

[0033] FIGS. 8 to 10 show the rear part of a shell which otherwise cancorrespond to the shell 1 a in FIG. 1. In this variant, the rear part 41of the shell 1 a has a base-bleed unit which is generally labelled 42.Immediately in front of the base-bleed unit 42 there is a track in theshell body in which the plastic drive band 43 of the shell 1 a ismounted. The base-bleed unit 42 comprises a number of powder chambers 44which in cross section have a circular sector shape (see FIG. 9) andeach initially includes a slow-burning powder and a central gas outlet45. FIGS. 8 and 10 show the position after the shell 1 a (which is notshown in its entirety in the figures) has just left the barrel of theartillery piece. A number of deployable fins 46-51 are also arranged insaid rear part 41 of the shell. These fins are shown in the retractedposition in FIGS. 8 and 9 and in the deployed position in FIG. 10. Eachof the fins consists of an inner primary fin 52, which can be retractedinto the shell body or more precisely into the base-bleed unit 42, and asecondary fin 53 which can be telescoped into the primary one. Each ofthe primary fins 52 is radially controlled and radially displaceablebetween supporting and protecting walls 54 and 55, respectively,arranged on either side of it (see FIG. 9), and since the innerlongitudinal edges 56 of the primary fins 52 additionally have freecontact with the inside of the powder chamber 44, the primary fins 52start to move, as soon as they are allowed to, after the shell has leftthe barrel and the casing 58 has been removed, forced out by theremaining barrel pressure through respective slits 57 in the shell bodyby the remaining pressure from the barrel phase, possibly supplementedby the pressure from the ignited base-bleed powder. The secondary fins53 are correspondingly mounted and are displaceable in the primary fins52 and thus are also dependent on the powder gas pressure in the powderchamber 44 for their deployment. Until the moment when the shell 1 a hasleft the barrel of the artillery piece in connection with the launchphase, allowing for a slight margin, both the base-bleed unit 42 and theretracted fins are covered by a protective casing 58. FIG. 8 shows aposition in which the protective casing 58 has begun to be pushed awayfrom its original position. In the original position, the protectivecasing 58 covers the whole of the base-bleed unit 42. The pushing-off ofthe casing and the deployment of the fins are activated in thepreviously described manner by that part of the propellant gas pressurewhich has been allowed during the launch phase to leak into the insideof the casing and the base-bleed unit 42 via the opening 61.

[0034] At the same time as or immediately after the protective casing 58is removed, the powder charge of the base-bleed unit is initiated, andat the same time the remaining pressure from the barrel phase is used toforce out the fin parts. When the primary fins 52 reach their respectiveouter positions, their respective inner longitudinal edges 56 seal thegap in the base-bleed unit wall through which they are deployed and atthe same time the gas pressure also forces out the secondary fins 53 toa correspondingly sealed and blocked outer position.

[0035] As can be seen principally from FIG. 9, the inner primary fins 52in the retracted position are surrounded on each side by the previouslymentioned protective walls 54, 55 which form part of atemperature-resistant lining 59 of the powder chamber 44 of thebase-bleed unit and which thus in pairs of two adjoining fins divide upthe powder chamber into a number of sectors or fissures which eachoriginally contain a suitable quantity of powder or powder body. Alsoarranged at the centre of the unit there is a central powder gas andignition channel 60 which is common to all the powder chamber sectors tothe extent that these open into the latter. As has already beenmentioned, the inlet of the casing 58 has been labelled 61.

[0036] Since each of the powder sectors has in this way been able to begiven a limited size and a good lateral support between the protectivewalls 54, 55 of the adjoining primary fins 52, it has been possible toeliminate the risks of the powder charge in the base-bleed unit beingdamaged during actual firing, that is to say before it is brought intooperation, and at the same time the division gives the powder bodies ahigh level of strength right up to the time they burn out.

1. Method applied to missiles fired from launch weaponry, for exampleshells (1 a, 1 b) etc., and using some of the powder gases generated inthe barrel during the launch phase for an additional active functionover and above that of giving the shell (1 a, 1 b) in question itstrajectory velocity, characterized in that, during the launch phase,some of the propellant powder gas accelerating the shell is introducedinto a chamber (12, 38, 60) which is arranged in the same and which isdelimited in at least one direction by an element (8, 31, 58, 52, 53)which is movable relative to the rest of the shell and on which thebarrel pressure acting on the shell simultaneously acts to maintain theoriginal direction as long as the shell is located inside the barrelduring the launch phase, after which the propellant gases in the chamberare used, as soon as the external counterpressure ceases, to activate anactive displacement between two components included initially in themissile.
 2. Method according to claim 1, characterized in that thepropellant powder gases introduced into said chamber inside the shell (1a, 1 b) are used to activate and force through a relative displacementbetween the main part of the shell (1 a, 1 b) and said movable elements(8, 31, 58, 52, 53) immediately after the shell has left the barrel andthe counterpressure of the propellant powder gases has begun to beequalized in relation to the atmospheric pressure.
 3. Method accordingto claim 1 or 2, characterized in that the propellant powder gases areintroduced into said chamber (12, 38, 60) via an inlet (13, 39, 61)which is dimensioned in such a way that, when the counterpressure dropsto normal atmospheric pressure outside the barrel, the propellant powdergases introduced at high pressure into said chamber do not have time tobe equalized at the same rate but instead give rise to the desiredrelative displacement.
 4. Method according to any of claims 1-3 inwhich, after said shell (1 a, 1 b) has been fired from the barrelprovided for this purpose, a protective casing (8, 58) is removed whichduring the launch phase covers at least part of the rear part of theshell (1 a, 1 b) situated behind the drive band (2, 43) of the shell,characterized in that some of the powder gases driving the shell throughthe barrel in the launch phase are allowed to leak into a space (12, 60)provided for this purpose inside the protective casing (8, 58). 5.Method according to any of claims 1-3 in which, after a shell (1 a, 1 b)has been launched from a barrel provided for this purpose, it ispossible for a fin unit (31), initially located inside the shell, to bepushed rearwards relative to the direction of flight of the shell to thetrajectory position of the fin unit, with the fins (32) behind the rearplane of the shell (1 b) during the launch phase, characterized in thatsome of the propellant powder gases driving the shell (1 b) through thebarrel are introduced during the launch phase into a chamber (38) whichis arranged inside the shell and whose boundary wall forms part of thefin unit (31) which is axially movable within the shell and on whoseopposite side the barrel pressure acts for as long as the shell (1 b) islocated inside the barrel during the launch phase.
 6. Method accordingto any of claims 1-3 in which, after a shell (1 a) has been launchedfrom a barrel provided for this purpose, it is possible to deploy aplurality of fins (52, 53) which are arranged in the rear part of theshell and which, from a retracted position, can be forced out transverseto the direction of flight of the shell, characterized in that duringthe launch phase the fins (52, 53) are kept retracted by a casing (58)covering the rear part of the shell, in that this casing is removed bymeans of some of the powder gases driving the shell being introducedinto the casing (58) during the launch phase, and in that after thecasing has been removed the remaining powder gas pressure is used toforce out the fins (52, 53).
 7. Arrangement which can be used, inconjunction with the method according to any of claims 1-6, in shells (1a, 1 b) fired from launch weaponry, using the barrel pressure built upin the barrel during the launch phase to implement an active functionover and above that of giving the shell the necessary trajectoryvelocity, characterized in that it comprises a chamber (12, 38, 60)which is arranged inside the shell and which is delimited in at leastone direction by a movable object (8, 58, 31, 52, 53) which, in theoriginal position during the launch phase of the shell from the barrel,is acted upon from outside by the propellant powder pressure in thebarrel, and an inlet (61) which leads to said chamber from that part ofthe shell which, viewed in the direction of flight, is situated behindits drive band (43), and through which inlet (61) some of the barrelpressure during the launch phase gains access to the chamber (60). 8.Arrangement according to claim 7, characterized in that said inlet (61)is so dimensioned that the pressure which is able to build up inside thechamber (60) during the launch phase of the shell (1 a), by means ofpropellant gases leaking into the chamber after the shell has left thebarrel and the barrel pressure behind the shell is equalized in relationto the atmospheric pressure, cannot be regulated in the same way beforesaid movable object (52, 53) has been displaced by the same pressure tothe desired final position.